They're a blast, they're flashy, and they target a bunch of common goals for compare/contrast. They also make one for categories that I have - that one is pretty great as well!
I don't know if it's the double dice that make it fun, or that I turn it into a Family Feud-style game show every time I use these, but the kids are always into it!
I did see on their website that they have a book filled with worksheets that can be used with the dice...that may be my next purchase! I will of course report back! :)
Price-wise I think it's pretty reasonable. Each add-on deck retails for $16.99. You can buy a pack of 2 double dice for $11.95.
The link for the deck is HERE.
The link for the dice is HERE.